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  • PANGAEA  (222)
  • Elsevier  (53)
  • China Geological Survey  (5)
  • GEOMAR Helmholtz-Zentrum für Ozeanforschung Kiel  (3)
Document type
Keywords
Publisher
Years
  • 11
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    Benthic respiration and energy transfer in cold seep habitats (2009)
    Elsevier
    In:  [Talk] In: Goldschmidt Conference 2009 "Challenges to Our Volatile Planet", 21.-26.06.2009, Davos, Switzerland ; A1249 .
    Details
    Publication Date: 2019-09-23
    Type: Conference or Workshop Item , NonPeerReviewed
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    OceanRep: Talk
  • 12
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    A possible long-term CO2 sink through submarine weathering of detrital silicates (2006)
    Elsevier
    In:  Geochimica et Cosmochimica Acta, 70 (18,Suppl. 1). A11.
    Details
    Publication Date: 2017-09-08
    Description: The weathering of silicate minerals exposed on the continents is the largest sink of atmospheric CO2 on time scales of millions of years. The rate of this process is positively correlated with global mean temperature and atmospheric CO2 concentration, resulting in a negative feedback that stabilizes Earths’ climate (Berner, 2004). Detrital silicates derived from the physical denudation of the continents are a major component of marine sediments (Li and Schoonmaker, 2003). However, their geochemical behaviour is poorly understood and they are considered to be unimportant to the long-term carbon cycle. We show that in organic matter-rich sediments of the Sea of Okhotsk detrital silicates undergo intense weathering. This process is likely favoured by microbial activity, which lowers pore water pH and releases dissolved humic substances, and by the freshness of detrital silicates which originate from the cold, poorly weathered Amur River basin. Numerical simulations of early diagenesis show that submarine weathering rates in our study area are comparable to average continental weathering rates (Gaillardet et al., 1999). Furthermore, silicate weathering seems to be widespread in organic matter-rich sediments of continental margins, suggesting the existence of a significant CO2 sink there. These findings imply a greater efficiency of the silicate weathering engine also at low surface temperatures, resulting in a weakening of the negative feedback between pCO2, climate evolution and silicate weathering.
    Type: Article , NonPeerReviewed
    Format: text
    DOI: 10.1016/j.gca.2006.06.035
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    OceanRep: Article in a Scientific Journal - without review
  • 13
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    Mineralische Rohstoffe aus der Tiefsee - Entstehung, Potential und Risiken (2019)
    GEOMAR Helmholtz-Zentrum für Ozeanforschung Kiel
    In:  GEOMAR Helmholtz-Zentrum für Ozeanforschung Kiel, Kiel, Germany, 34 pp.
    Details
    Publication Date: 2020-11-18
    Type: Report , NonPeerReviewed
    Format: text
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    OceanRep: Report - other report
  • 14
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    Gas release experiment (2012)
    GEOMAR Helmholtz-Zentrum für Ozeanforschung Kiel
    In:  In: RV Celtic Explorer EUROFLEETS cruise report CE12010 - ECO2@NorthSea : 20.07. – 06.08.2012, Bremerhaven - Hamburg. , ed. by Linke, P. GEOMAR Helmholtz-Zentrum für Ozeanforschung Kiel, Kiel, pp. 28-32.
    Details
    Publication Date: 2014-02-20
    Type: Book chapter , NonPeerReviewed
    DOI: 10.3289/GEOMAR_REP_NS_4_2012
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    OceanRep: Book chapter
  • 15
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    Spatial variation in fluid flow and geochemical fluxes across the sediment–seawater interface at the Carlos Ribeiro mud volcano (Gulf of Cadiz) (2011)
    Elsevier
    In:  Geochimica et Cosmochimica Acta, 75 (4). pp. 1124-1144.
    Details
    Publication Date: 2017-09-27
    Description: Submarine mud volcanism is an important pathway for transfer of deep-sourced fluids enriched in hydrocarbons and other elements into the ocean. Numerous mud volcanoes (MVs) have been discovered along oceanic plate margins, and integrated elemental fluxes are potentially significant for oceanic chemical budgets. Here, we present the first detailed study of the spatial variation in fluid and chemical fluxes at the Carlos Ribeiro MV in the Gulf of Cadiz. To this end, we combine analyses of the chemical composition of pore fluids with a 1-D transport-reaction model to quantify fluid fluxes, and fluxes of boron, lithium and methane, across the sediment–seawater interface. The pore fluids are significantly depleted in chloride, but enriched in lithium, boron and hydrocarbons, relative to seawater. Pore water profiles of sulphate, hydrogen sulphide and total alkalinity indicate that anaerobic oxidation of methane occurs at 34–180 cm depth below seafloor. Clay mineral dehydration, and in particular the transformation of smectite to illite, produces pore fluids that are depleted in chloride and potassium. Profiles of boron, lithium and potassium are closely related, which suggests that lithium and boron are released from the sediments during this transformation. Pore fluids are expelled into the water column by advection; fluid flow velocities are 4 cm yr−1 at the apex of the MV but they rapidly decrease to 0.4 cm yr−1 at the periphery. The associated fluxes of boron, lithium and methane vary between 7–301, 0.5–6 and 0–806 mmol m−2 yr−1, respectively. We demonstrate that fluxes of Li and B due to mud volcanism may be important on a global scale, however, release of methane into the overlying water column is suppressed by microbial methanotrophy.
    Type: Article , PeerReviewed
    Format: text
    Format: text
    DOI: 10.1016/j.gca.2010.11.017
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 16
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    Sources of fluids and gases expelled at cold seeps offshore Georgia, eastern Black Sea (2011)
    Elsevier
    In:  Geochimica et Cosmochimica Acta, 75 (11). pp. 3250-3268.
    Details
    Publication Date: 2019-06-27
    Description: Four seep sites located within an -20 km2 area offshore Georgia (Batumi seep area, Pechori Mound, Iberia Mound, and Colkheti Seep) show characteristic differences with respect to element concentrations, and oxygen, hydrogen, strontium, and chlorine isotope signatures in pore waters, as well as impregnation of sediments with petroleum and hydrocarbon potential. All seep sites have active gas seepage, near surface authigenic carbonates and gas hydrates. Cokheti Seep, Iberia Mound, and Pechori Mound are characterized by oil-stained sediments and gas seepage decoupled from deep fluid advection and bottom water intrusion induced by gas bubble release. Pechori Mound is further characterized by deep fluid advection of lower salinity pore fluids. The Pechori Mound pore fluids are altered by mineral/water reactions at elevated temperatures (between 60 and 110°C) indicated by heavier oxygen and lighter chlorine isotope values, distinct Li and B enrichment, and K depletion. Strontium isotope ratios indicate that fluids originate from late Oligocene strata. This finding is supported by the occurrence of hydrocarbon impregnations within the sediments. Furthermore, light hydrocarbons and high molecular weight impregnates indicate a predominant thermogenic origin for the gas and oil at Pechori Mound, Iberia Mound, and Colkheti Seep. C15+ hydrocarbons at the oil seeps are allochtonous, whereas those at the Batumi seep area are autochthonous. The presence of oleanane, an angiosperm biomarker, suggests that the hydrocarbon source rocks belong to the Maikopian Formation. In summary, all investigated seep sites show a high hydrocarbon potential and hydrocarbons of Iberia Mound, Colkheti Seep, and Pechori Mound are predominantly of thermogenic origin. However, only at the latter seep site advection of deep pore fluids is indicated.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/j.gca.2011.03.018
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 17
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    Spatial and temporal modelling of thermal effects during CO2 injection into methane-hydrate reservoirs (2014)
    China Geological Survey
    In:  [Paper] In: 8. International Conference on Gas Hydrates (ICGH8), 28.07.-01.08.2014, Beijing, China . Proceedings of the 8th International Conference on Gas Hydrates (ICGH8-2014), Beijing, China, 28 July - 1 August, 2014 ; T3-56 .
    Details
    Publication Date: 2016-12-21
    Description: Injection of CO2 into CH4-hydrate bearing sediments, and the resulting in-situ replacement of CH4-hydrate by CO2-hydrate, has been proposed as a technique for the emission-free production of natural gas from gas hydrates. While the hydrate conversion is thermodynamically feasible, many studies conclude that the overall process suffers from mass transfer limitations and CH4 production is limited after short time. To improve CH4 production various technical concepts have been considered, including the injection of heated supercritical CO2 combining chemical activation and thermalstimulation. While the feasibility of the concept was demonstrated in high-pressure flow-through experiments and high CH4 production efficiencies were observed, it was evident that overall yields and efficiencies were influenced by a variety of processes which could not be disclosed through bulk mass and volume analysis. Here we present different numerical simulation strategies which were developed and tested as tools to better understand the importance of mass and heat transport relative to reaction and phase transition kinetics for CH4 release and production, or for CO2 retention, respectively. The modeling approaches are discussed with respect to applicability for experimental design, process development or prediction of CH4 production from natural gas hydrate reservoirs on larger scales.
    Type: Conference or Workshop Item , NonPeerReviewed
    Format: text
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    OceanRep: Conference paper
  • 18
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    Experimental investigation of water permeability in quartz sand as function of CH4-hydrate saturation (2014)
    China Geological Survey
    In:  [Paper] In: 8. International Conference on Gas Hydrates (ICGH8), 28.07.-01.08.2014, Beijing, China . Proceedings of the 8th International Conference on Gas Hydrates (ICGH8) Beijing, China, 28 July - 1 August, 2014 ; T1-68 .
    Details
    Publication Date: 2014-11-21
    Description: Water permeability in gas hydrate bearing sediments is a crucial parameter for the prediction of gas production scenarios. So far, the commonly used permeability models are backed by very few experimental data. Furthermore, detailed knowledge of the exact formation mechanism leads to severe uncertainties in the interpretation of the experimental data. We formed CH4 hydrates from a methane saturated water solution and used Magnetic Resonance Imaging (MRI) to measure time resolved maps of the three-dimensional gas hydrate saturation. These maps were used for 3D Finite Elements Method (FEM) simulations. The simulation results enabled us to optimize existing models for permeabilities as function of gas hydrate saturation.
    Type: Conference or Workshop Item , NonPeerReviewed
    Format: text
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    OceanRep: Conference paper
  • 19
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    Rising methane gas bubbles form massive hydrate layers at the seafloor (2004)
    Elsevier
    In:  Geochimica et Cosmochimica Acta, 68 (21). pp. 4335-4354.
    Details
    Publication Date: 2017-09-08
    Description: Extensive methane hydrate layers are formed in the near-surface sediments of the Cascadia margin. An undissociated section of such a layer was recovered at the base of a gravity core (i.e. at a sediment depth of 120 cm) at the southern summit of Hydrate Ridge. As a result of salt exclusion during methane hydrate formation, the associated pore waters show a highly elevated chloride concentration of 809 mM. In comparison, the average background value is 543 mM. A simple transport-reaction model was developed to reproduce the Cl- observations and quantify processes such as hydrate formation, methane demand, and fluid flow. From this first field observation of a positive Cl- anomaly, high hydrate formation rates (0.15–1.08 mol cm-2 a-1) were calculated. Our model results also suggest that the fluid flow rate at the Cascadia accretionary margin is constrained to 45–300 cm a-1. The amount of methane needed to build up enough methane hydrate to produce the observed chloride enrichment exceeds the methane solubility in pore water. Thus, most of the gas hydrate was most likely formed from ascending methane gas bubbles rather than solely from CH4 dissolved in the pore water.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/j.gca.2004.01.018
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 20
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    Quantification of methane emissions at abandoned gas wells in the Central North Sea (2015)
    Elsevier
    In:  Marine and Petroleum Geology, 68 . pp. 848-860.
    Details
    Publication Date: 2017-12-19
    Description: As a result of extensive hydrocarbon exploration, the North Sea hosts several thousand abandoned wells; many believed to be leaking methane. However, how much of this greenhouse gas is emitted into the water column and ultimately reaches the atmosphere is not known. Here, we investigate three abandoned wells at 81-93m water depth in the Norwegian sector of the North Sea, all of which show gas seepage into the bottom water. The isotopic signature of the emanating gas points towards a biogenic origin and hence to gas pockets in the sedimentary overburden above the gas reservoirs that the wells were drilled into. Video-analysis of the seeping gas bubbles and direct gas flow measurements resolved initial bubble sizes ranging between 3.2 and 7.4mm in diameter with a total seabed gas flow between 1 and 19 tons of CH4 per year per well. Estimated total annual seabed emissions from all three wells of ~24 tons are similar to the natural seepage rates at Tommeliten, suggesting that leaky abandoned wells represent a significant source of methane into North Sea bottom waters. However, the bubble-driven direct methane transport into the atmosphere was found to be negligible (〈2%) due to the small bubble sizes and the water depth at which they are released.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
    DOI: 10.1016/j.marpetgeo.2015.07.030
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    OceanRep: Article in a Scientific Journal - peer-reviewed
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